This invention relates to a new aerodynamic concept of aircraft based on flying wing idea that had emerged around 80 years ago, which anticipates the elimination of all surfaces that are not generating lift in order to minimize wetted area with a simultaneous increase of airlifting area, thus increasing the lift capacity, as well as minimizing aerodynamic drag and fuel consumption of aircraft.
For the past 80 years, we have seen a large number of different ideas as to how to practically realize this idea in the most effective way. Some of the relevant ideas may be found among sited references. Unfortunately, no such idea has risen up to a sufficiently high level to meet safety requirements and official regulations for civil air transportation with competitive aerodynamic efficiencies relative to classical concept aircraft at high subsonic speeds. There have been two main obstacles that resulted with such outcome including difficulties related to attaining the efficient longitudinal stabilization and pitch control of a large airlifting body, as well as the effective accommodation of bulky payload within the airlifting body that is designed with thin efficient airfoils.
All prior art related to flying wing idea can be classified in two major groups: tailess flying wing aircraft and hybrid flying wing aircraft. Tailess flying wing aircraft have only a single integral airlifting body, which is simultaneously producing aerodynamic lift while longitudinally stabilizing itself in different flight conditions. This is an extremely ambitious goal from the flight mechanics perspective due to the fact that the above is achieved by natural fliers with the change of surface area and position of wings in all three planes, while additionally having a tailplane with the changeable area and position thereof for pitch control in various flight conditions. The integral rigid airlifting body of tailess flying wing aircraft can not meet several simultaneous and contradictory requirements including natural dynamic and static stability when the airlifting body is designed with efficient aft camber airfoils that have air pressure center shifted in aft direction while having inability to deploy trailing edge devices for extra lift production at low sped during take-off and landing due to high negative pitch momentum. Tailess flying wing aircraft are having the position of their neutral point approximately at around 25% of mean geometric chord of integral airlifting body. The gravity center of natural dynamically stable aircraft needs to be positioned in longitudinal direction in front of neutral point. This consequently requires the integral airlifting body to be defined with low efficient reflex airfoils that have air pressure center shifted in front of 25% of airfoil chord to satisfy the static stability of aircraft in cruising conditions when trailing edge devices for aerodynamic lift regulation being in the neutral position. The low aerodynamic efficiency of such aircraft is especially pronounced at high subsonic and transonic speeds. If the integral airlifting body of a tailess flying wing aircraft was designed with efficient aft camber airfoils, the aircraft gravity center would need to be shifted in aft direction behind the neutral point in order to satisfy the static stability of aircraft when trailing edge devices for aerodynamic lift regulation being in their neutral position, thus such aircraft being naturally dynamically unstable, hence not satisfying safety regulations for civil air transportation.
In both cases, trailing edge devices for extra lift production can not be used due to a high negative pitch momentum that would be generated, hence requiring a high attack angle during approach to the airport and landing phase, thus additionally jeopardizing the flight safety and ride quality of such aircraft.
Military bomber B-2 is an example of a dynamically unstable tailess flying wing aircraft that has been fully developed so far though at extremely high production cost with limited range and speed, as well as low flight safety, all of which are the reasons for a low number of units that have been manufactured.
The Blended Wing Body aircraft is one of the most recent attempts to apply tailess flying wing concept to civil applications. Intensive research over the past 15 years that has involved a significant number of experts in the areas of theoretical and applied aerodynamics, as well as computational analysis and wind tunnel testing have not produced a desirable outcome to simultaneously satisfy a required level of flight safety and competitive aerodynamic efficiency for civil air transportation at high subsonic speeds.
Hybrid flying wing concepts assume the aircraft with two or more airlifting bodies that are mutually linked by aerodynamically shaped rigid connecting bodies. They further anticipated the accommodation of the payload within such airlifting bodies. These concepts are more flexible for aerodynamic optimization than tailess flying wing concepts. Hybrid flying wing concepts usually anticipate front and rear airlifting bodies. Front airlifting bodies are larger and except for lift production additionally providing for an inner space for payload accommodation. Rear airlifting bodies are used for longitudinal stabilization of aircraft, while providing for efficient pitch control and additional lift production. Rigid connected bodies may have other functions related to the flight control of an aircraft. There are a number of ideas and patents related to the hybrid versions of flying wing idea some of which are cited as references in this patent application. The most recent attempt for the affirmation of the hybrid fling wing concept has been presented in U.S. Pat. Nos. 6,923,403 and 7,793,884.
The “Tailed Flying Wing Aircraft” idea as outlined in U.S. Pat. No. 6,923,403 reflects a large front airlifting body with a semi-elliptical aft extension of the central trailing edge, whereby the upper section of the aerodynamic covers of jet engines is structurally directly integrated with the upper side of the airframe of the airlifting body in such a way that the upper surface of the airlifting body is enveloping the jet engine airintake on the lower side thereof. The tailplane as the rear airlifting and stabilizing body is connected to the front airlifting body either directly via the airframe of jet engine covers or by means of fin with rudder while being fastened to the jet engine cover. However, both solutions can not provide for a sufficient distance of the tailplane behind the large front airlifting body to allow for the application of efficient aft camber airfoil on the front airlifting body with a reasonable surface area of the tailplane due to a large semi-elliptical aft section of the front airlifting body that does not shift enough jet engine covers with stabilizing surfaces in aft direction, while simultaneously significantly increasing the area of the front airlifting body, which needs to be longitudinally stabilized. In addition, the thick turbulent boundary layer over the upper surface of the front airlifting body in front of jet engine air intake is significantly reducing the jet engine efficiency of the “Tailed Flying Wing Aircraft” when compared with the efficiency of the jet engines of classical concept aircraft, which are positioned in front of wings, hence encountering a free and undisturbed airflow.
The “T-tailed Deltoid Main Wing Aircraft” idea as outlined in U.S. Pat. No. 7,793,884 reflects a number of improvements relative to “Tailed Flying Wing Aircraft” concept. A deltoid shape of the rear portion of the central section of front airlifting body that is defined with a straight trailing edge is strengthened with an aerodynamically shaped extended vertical aft reinforcement, whose fin with a tailplane on the top thereof is fastened thereto, hence resulting with a much longer distance of the tailplane aft of the front airlifting body with a smaller airlifting area thereof when compared to “Tailed Flying Wing Aircraft” with the same payload capacity. This configuration provides for the static stability of “T-tailed Deltoid Main Wing Aircraft” in cruising conditions when the front airlifting body and tailplane are designed with efficient aft-camber airfoils, while having a relatively small wetted area and low negative aerodynamic loading of the tailplane. Additionally, jet engines with air intake are positioned above the upper surface of the front airlifting body via jet engine pylons to avoid the turbulent boundary layer of the front airlifting body. However, still a large wetted area of the tailplane when compared to classical concept aircraft, which does not produce lift or producing even a small amount of negative lift, as well as the parasite wetted area of fin with rudder and jet engine pylons with nacelles that are not contributing to lift production or longitudinal stabilization of aircraft may not be resulting with overwhelming advantages of flying wing idea over the classical concept aircraft with fuselage at high subsonic speeds.